insulin human

short-acting insulin· Brands: Humulin R, Novolin R, Actrapid, Insuman RapidIVSC

Mechanism of action

Insulin human binds to the insulin receptor on target cells (muscle, adipose, liver), activating a tyrosine kinase cascade. This promotes translocation of GLUT4 transporters to the membrane, increasing glucose uptake; it also stimulates glycogen synthesis, lipogenesis, and protein synthesis, while inhibiting hepatic gluconeogenesis and glycogenolysis. Overall, it lowers blood glucose and promotes anabolic metabolism.

Pharmacokinetics

After subcutaneous injection, onset of action is typically 30 minutes, peak effect occurs at 1-2 hours, and duration is about 4-6 hours. Absorption is influenced by injection site, depth, and blood flow. Insulin is metabolized mainly in the liver, with some renal clearance. The plasma half-life is short, around 4-6 minutes, but the biologic effect lasts longer. Intravenous administration yields immediate onset and short duration.

Indications & dosing

Type 1 diabetes mellitus

As part of basal-bolus regimen, adjust according to glucose monitoring and carbohydrate intake.

adult · SC: 0.1–0.2 units/kg before meals · As part of basal-bolus regimen, adjust according to glucose monitoring and carbohydrate intake.

Type 2 diabetes mellitus

Use in combination with basal insulin or as prandial replacement; individualise.

adult · SC: 0.1–0.2 units/kg before meals · Use in combination with basal insulin or as prandial replacement; individualise.

Diabetic ketoacidosis

Continuous IV infusion; monitor glucose, ketones and electrolytes carefully.

adult · IV: 0.1 units/kg/hr continuous · Continuous IV infusion; monitor glucose, ketones and electrolytes carefully.

Hyperkalemiaoff-label

Administer with 25-50 g glucose to prevent hypoglycaemia; monitor glucose and potassium.

adult · IV: 10–15 units single dose · Administer with 25-50 g glucose to prevent hypoglycaemia; monitor glucose and potassium.

Contraindications & precautions

Hypoglycaemia · Insulin administration during an episode of hypoglycaemia would worsen the condition.
Hypersensitivity to insulin human or any excipients · May cause anaphylaxis. Check for cross-reactivity with other insulins.
Renal impairment · Insulin clearance may be reduced, increasing the risk of hypoglycaemia; dose reduction may be required.
Hepatic impairment · Reduced gluconeogenesis and insulin metabolism may increase the risk of hypoglycaemia; monitor closely.
Monitor blood glucose regularly and adjust the insulin dose based on individual response, diet, and exercise.
Rotate injection sites to avoid lipodystrophy and ensure consistent absorption.
Be alert for signs of hypoglycaemia, such as sweating, palpitations, tremor, and confusion; advise patients to carry a fast-acting carbohydrate.
Use caution in patients with renal or hepatic impairment; dose reduction may be necessary.
When switching from another insulin brand or type, monitor closely due to differences in onset and duration of action.

Adverse effects

Hypoglycaemiaserious
Weight gain
Injection site reactions (including lipodystrophy)
Hypokalaemiaserious
Anaphylaxisserious

Interactions

propranololmajorMonitor blood glucose more frequently, especially when starting, stopping, or changing the dose of propranolol. Educate the patient about atypical symptoms of hypoglycaemia, such as sweating or a sense of weakness without tachycardia. Consider using a cardioselective beta-blocker (e.g., atenolol or metoprolol) which may be less likely to mask symptoms, though caution is still advised. Adjust insulin doses as necessary, and advise the patient to carry a source of fast-acting glucose. In high-risk patients, consider advising home glucose monitoring and carrying glucagon.

Monitoring, pregnancy & toxicity

Blood glucose · Frequently, especially after initiation or dose changes
HbA1c · Every 3-6 months
Serum potassium · During dose adjustments, especially when used with other medications affecting potassium
Signs of hypoglycaemia · Regularly; educate the patient
Weight · Periodically
Injection sites · Rotate sites with each injection
Pregnancy: Insulin human is the preferred insulin for diabetes in pregnancy; it does not cross the placenta and is safe for both mother and fetus. Tight glycaemic control is important to reduce maternal and fetal complications.
Toxicity: Hypoglycaemia (sweating, tremors, palpitations, confusion, seizures, coma) · Mild: oral glucose 15-20 g. Severe: IV glucose 10-25 g, or IM/SC glucagon 1 mg; repeat as needed.

Antidotes & reversal

Dextrose 10-50% IV · IV dextrose for hypoglycaemia; glucagon IM if no IV access; prolonged observation after large doses.

Clinical notes

Used for the management of diabetes mellitus, particularly for acute hyperglycaemia, diabetic ketoacidosis, and perioperative control. It is also used in hyperkalaemia with glucose. Dose must be individualized based on blood glucose monitoring. Hypoglycaemia is the main adverse effect; patients must be educated on recognition and treatment. When switching between species, doses may need adjustment. Store unopened vials in the refrigerator; in-use vials may be kept at room temperature.

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BNF; local formulary